1. Field of the Invention
This invention relates to the structures of operative parts of rotating members, and more particularly to the structure of an operative part of a rotating member which is suitable for a winding key which is formed at the end of a spring winding shaft, such as in a music box.
2. Related Art
A rotating operation member is used for a winding key formed on the end portion of a spring winding shaft.
For example, as shown in FIGS. 4 (a) and (b), a power spring 130 fixed in a box 120 is wound around a winding member 140 so that the power spring 130 serves as a power source for driving a speed governor to adjust the speed of a rotating dram 150. A plurality of pins 170 repel a respective plurality of vibration plates to produce music. A winding key is screwed to a lower end portion of the winding member 140.
A conventional winding key adapted to wind a spring, such as in a musical box, is shown in FIG. 3 (a). The key includes a connecting member 41, and a handle member 5 which is engaged with a through-hole 41 formed in one end portion of the connecting member 4. The handle member 5 includes an arcuate knob portion 51 for turning the handle member and the connecting member to which the handle is connected, a pair of bent portions 54 and 55 which are extended from both ends of the arcuate knob 51 and bent inwardly, and a pair of protruded portions 52 and 53 which are formed at the ends of the bent portions 54 and 55 in such a manner that they are extended towards each other. The protruded portions 52 and 53 are fitted in respective end openings 42 and 43 of the through-hole 41 in the connecting member 4, so that the handle member 5 is coupled to the connecting member 4 in such a manner that it is swingable about the common central axis of the protruded portions 52 and 53. The other end portion of the connecting member 4 includes a threaded portion 44 which is engaged with a spring winding shaft.
When the winding key is not used, the knob portion 51 is swung over the side surface of the spring winding shaft. Hence, before the winding key is operated, the knob portion 51 is swung back in line with the axis of the spring winding shaft. The knob portion 51 is then turned around the axis of the spring winding shaft to wind the spring.
In the above-described conventional winding key, the connecting member 4 and the handle member 5 are in contact with each other through the edges of the openings of the through-hole 41 and the flanges which are formed around the protruded portions. Since the contact parts of members 4 and 5 are considerably unstable in contact pressure, the handle member 5 may not be smoothly turned, which can result in an injury to the operator's fingers and/or excessive vibration noise. Furthermore, the torque required for swinging the handle member 5 (hereinafter referred to as "swing torque") may not be consistent from one key to the next, some of the components may have different dimensions when manufactured. In other words, different winding keys may have different swing torques. In addition, the torque may vary depending on the angle of swing of the handle member because of dimensional errors of in machining the components. When the winding key is used frequently, the contact parts of the connecting member 4 and the handle member 5 are worn and deformed, which results in an increase in contact pressure. If the contact parts are non-uniformly worn, it may become difficult or impossible to swing the handle member from one position to another.
For instance, in the case as shown in FIG. 3 (b), the periphery 43a of the opening of the connecting member 4 is variable in height in a circumferential direction, and the contact pressure changes depending on the difference d in height. This makes it impossible to smoothly swing the handle member 5. In the case shown in FIG. 3 (c), where the periphery 43a' of the opening is in contact with the handle member 5 through an edge F, the contact parts are severely worn as the winding key is used.